Mycoplasma hyopneumoniae-specific IgG and IgA levels in sows and piglets. Farm A: endemically infected with M. hyopneumoniae; Farm B: free of M. hyopneumoniae. A, B: individual levels in serum of sows; C, D: individual levels in colostrum of sows; E, F: average levels in serum of 2-day-old piglets (4 piglets per sow on farm A; 8 piglets per sow on farm B). On farm A, sows (n = 6) were vaccinated against M. hyopneumoniae at 6 and 3 weeks before farrowing and blood samples were taken before the first vaccination (pre vacc.) and at the time of farrowing (post vacc.). On farm B, blood of the sows (n = 3) was sampled at the time of farrowing. Color coding of the piglets corresponds to the color of their mother of which they ingested colostrum. Red line: cut-off optical density value for positive samples.